Ancestors of modern Indians may have come to Australia before Europeans, genetic study shows

LONG before Australia and India faced off on the cricket pitch, people from the subcontinent arrived on our shores and bred with Aborigines, scientists report.

A genetic study has found ancestors of modern Indians may have come to Australia about 4000 years before Europeans colonised the continent.

Modern humans are thought to have arrived down under about 40,000 years ago, having made their way out of Africa around the coast of the Arabian Peninsula and India to Australia.

Most scientists believed these ancestors of modern Aborigines remained isolated from other populations until Europeans appeared in the late 18th century.

But a genetic analysis of more than 300 Aborigines, Indians and people from Papua New Guinea and island south-east Asia has found a ''significant gene flow'' from India to Australia about 4230 years, or 141 generations, ago.

The study's lead researcher, Irina Pugach, from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, said the arrival of these people during the period known as the Holocene coincided with many changes in Australia's archaeological record.

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''[There was] a sudden change in plant processing and stone tool technologies, with microliths appearing for the first time, and the first appearance of the dingo in the fossil record,'' Dr Pugach said.

''Since we detect inflow of genes from India into Australia at around the same time, it is likely that these changes were related to this migration.''

Alan Cooper, the director of the Australian Centre for Ancient DNA at the University of Adelaide, said this early Indian movement was a ''complete mystery''.

The Aboriginal DNA used in the study comprised more than 10 per cent Indian genetic markers, which suggested there had been substantial interbreeding between the groups. ''[The Indians] could have been sea traders,'' said Professor Cooper, who was not involved in the study.

The researchers said it was possible Indian ancestry came to Australia indirectly, through south-east Asian populations that had trade links with northern Australia and Indonesia. But the analysis found no evidence of this in the genes of the island south-east Asian populations.

The study also found a common origin between Aboriginal Australians, New Guinea populations and the Mamanwa - a Negrito group from the Philippines. The researchers estimate these groups split from each other about 36,000 years ago.

A study co-author, Mark Stoneking, said this finding, which is published in the Proceedings of the National Academy of Sciences journal, supported the view that these populations were the descendants of an early southern route migration out of Africa.